Won't idle when hot

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[John Jones Jr.]

Might be worth opening up the throttle body and compare with this vid below. Odds on, at 175k your throttle potentiometer is fairly worn and thus causing the problems. I'd have a look at the wiring loom on the t/b also.

http://www.youtube.com/watch?v=BTXaHIjHZB0

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[John Jones Jr.]

Well, water is a bastard. And if the problem was highlighted by water ingress(very possible) it may suggest it's a wiring loom or connection issue but either way you can be sure your T/b has seen better days. It could be 550 bucks well spent. Finger crossed.

[John Jones Jr.]

This Potentiometer reminds me alot of like a temperature rheostat or even better it reminds me of one of these slot car hand controllers I used to use alot as a kid racing slot cars. TI used to have to open up the controllers and mess with te contact points until it finally no longer worked well enough I had to buy new controllers.

http://slotcarillustrated.com/Products/PMcontroller/pic1.jpg

Ha, it was train sets for me. Use to open up the the transformer (dial type), give it a good old 'cleaning' and of course it never worked afterwards!

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[John Jones Jr.]

Well, Dean if it's any consolation you can be sure it's not just your car that has or will have this wiring problem. W202 owners should take note, especially on the earlier cars.

I'd say too you can be fairly sure this is the problem, also there's a very good chance the car will drive far better with the new T/B. Looking forward to an update.

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[John Jones Jr.]

Funny you mention vacuum pipes. Changed the FRP on my car last week and found two slits in the rubber pipe connector. Age is taking it toll sadly.

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Now I can get back to the fun stuff of modifying it. That resumes tomorrow morning (Evil smile)

[John Jones Jr.]

Delighted to hear.

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[John Jones Jr.]

Dean, I understand it always advisable to disconnect the battery for something like 20 mins after replacing a faulty part such as your T/b, Camshaft position sensor etc. Thus the engine ECU learns very quickly a new part has been fitted and I've also been informed it takes the guts of up 200 miles before the ECU has done it's relearning. So, if my info is correct it would make total sense what you are experiencing with your car now. I can say from first hand experience on my W202 when I replaced the Cam sensor and MAF the car drove even better after a long journey and that was not my imagination getting carried away.

[Vetruck]

Thank you John for helping confirm my assumptions. I am going to give it a little more time before I even try to clear the code with my scanner.

I like doing play by play descriptive post so it helps any future people troubleshooting a problem. I always try and document my exact steps.

I should also state that the battery was disconnected during the time I pulled the car apart to change the TB. I never work on electrical stuff witht he battery connected. I made sure the system was clean and clear of codes before I diconnected it and started the work two days ago. I even had to dig out my manual to reprogram my radio code.

[Vetruck]

Update- Car has been smooth as glass for several days now. I would officially call this problem fixed. I cleared the code /service engine light a day ago and it has not returned in about 60 miles of driving.

[taz069]

I got ya beat by 5 days!! Not lmao!! But I did replace several needed items. All coils,and wires. Just waiting for my replacement tb ,purge valve,tb boot, and different ovp to come in now. Will split my wiring harness on my old tb this evening. And get it rebuilt for a spare. Yes mine has the same problems you have listed and thanks for the info on your writeup!! Check with chim in the classified he'sparting out his 96 c280 sport!! That be where my parts arecoming from. His was running and got t-boned. Thanks again!!

[mbsickness]

Seems like there are quite a few members with throttle body issues recently. For those folks who end up looking for a replacement make sure the part number match. There are a few different ones used over the years and in my case it had to come from a non-ASR C280 from 94-95.

[Vetruck]

Seems like there are quite a few members with throttle body issues recently. For those folks who end up looking for a replacement make sure the part number match. There are a few different ones used over the years and in my case it had to come from a non-ASR C280 from 94-95.

Since you mentioned it, I also thought it was very suspicious that several people are having the same issues all about the smae time frame (years wise). Kind of tells ya that everyone is going to have this issue from wires falling apart probably regardless of mileage, its probably more of an age in time rather than miles. Even a car just sitting there in a garage with low miles will suffer the same fate in the same time poeriod as a high milage car. Good ol Mecedes Biodegradable wires- the fuckers should have had a recall on this the filthy bastards

[taz069]

I am not so much sure on the year thing. I cut my tb wiring harness open last night and the thing looked brand new. If I can figure out how to send a pic with this new DNA phone I will.

[mbsickness]

In preparation of a rebuilt throttle body I removed the existing one from the car and just out of curiosity sliced open the wire harness. Didn't look too bad but it did have bits of insulation missing and cracks all over. Taz069 consider yourself lucky to have an intact harness. Is it possible yours was replaced in the past?

[taz069]

Mb I doubt it was replaced. Seeing the previous owners drove it into the dirt. Mine is looking like either a bad coil inside the tb or the potentiometer on the throttle linkage side.

[Vetruck]

Mine was just gone. I mean you could hardly see any isulation even attached to the wires, like about 10% still there and the rest of it feel out like sand. What amazes me is I know the previous owner of my car very well. He is an 80 year old guy that just babied this car and always garaged it. I doubt the car ever went over 70 mph. He also lives in Huntington beach about 3 niles off the coast were it is always about 10* cooler than inland here in So Cal- but yet not too close where things get corrosive on car paint etc like the ocean front homes do. This car lived in a perfect climate and was driven mildly- yet the wires were gone.

[mbsickness]

Hate to admit I was hoping for more damage as the car doesn't run beyond an idle. I hope the rewired throttle body does the trick.

[taz069]

Got the tb from chim in Friday and between rain downpours finally got it installed. After a few sputters things cleared right up running like a top again. I did disconnect the battery for 20-30 min after install. I guess the computer had to relearn things. All good now. No codes. Now onto the next lil noise. Sounding like the flex disc on the drive shaft right behind the tranny. It starts slow and as speed increases so does the sound. The sound is coming from around the shifter area. Yeah another problem. Thanks Ve for the write up.

[Vetruck]

Interesting it did the same few sputter at first. Thanks for confirming that. It is definately then the computer relearning on initial test drive. My sputters went away after 2 start and stops- and what I did get was very minor.

Good luck with the next project Taz.

Im actually heading out as we speak to get my tires mounted onto my wheels. Ill have pics soon. Not going on the car until later this week though. I have to fit the new studs and locktire and let them cure ont he car overnight maybe on Wednesday this week if all goes as scheduled.

[taz069]

Just had the car up on ramps. My flex disc's look great! Now the surrounding heat insulation is a different story. Did some rigging, hehe. A old coat hanger and built a arc to support the sagging padding. So far so good. I def would hate to have to replace that padding!!! Omg at the things to be removed. Car sputtered again just swapped out the purge valve and the ovp. Letting it sit with the battery disconnected and gonna put the charger to the battery. After I walk the pups and have a cold one. Looking forward to the pics!!

[Vetruck]

I ususally remove crap off the bottom of a car over time of ownership. things like heat sheilds and lastic guards etc. I like a car that is more simple and easy access to work on. Case in point I just shitcanned my plastic rear control arm covers. Heat shield can be done with dynamat if it gets hot int he cockpit. I have some of that laying around I use for heat wrapping parts like starters etc, or just plain l removing OEM heat stuff like you idsribe and stategically placing the new dynamat.

Just back from getting the new tires mounted
1434

[taz069]

Car tagged and on the road and somewhat running smooth. It still has the intermittent stumble. Once it warms up it very rarely stumbles. Once in a while it does. Heading to AutoZone and going to have them put their scan tool on it. I have just about reached whits end. Now come to find out my front lower control arm rear bushings are on the way out. Not to mention getting some Lucas rear end gear oil for a change in rear end fluid today. Thinking about changing the fuel filter to see it this helps. I did put a new one on when I first got the car maybe some old residual crap in the tank has it partially blocked. Fingers crossed. After a year + I am starting to wonder if this lil project is worth it!!!!!!!

[Vetruck]

Give me more info. what rpm is it stumbling (ie- coming off idle, or none with steady throttle position...only when throttle position is changed? etc)

Is it the same exactly as it did prior to putting on Chim's TB?

[taz069]

It stumbles at around 2k with steady throttle. Now let me run this by ya. Just returned from AutoZone. Their code reader showed some new codes. 1 being p0325 and p0327 knock sensor. With this it could be low fuel pressure, defective sensor,wiring, or engine problems. Will check on all of this. Next is code p0441 evaporative emision system. Which could be loose fuel cap(not!!), evap canister or hose cracked, purge or vent solenoid defective, or vacum leak at engine(possible). And then we have code p0341 cam position sensor. It's new so I doubt that but one thing in their print out says cylinder misfire, check ignition system for bad plugs, wires, coils. Now I just replaced all of that. So possibly???? Hope this helps a lil Ve! Out to change the rear end fluid now with some Lucas 80-90w. Let me know.

[Vetruck]

Im not a real ECM/PCM guy at all, but I know enough about basics to make me real leary about the cam psition sensor has to be part of "when the injectors fire" and well as "when the ignition fires"

I do know and have experience with hall effect triggers (crank shaft triggers) that tell the ignition when to fire. I would greatly suspect the cam sensor is somewhat the same principle. and is a safer way to tell the engine if its safe to fire based on the condition of the timing chain.

[taz069]

Just found a old post in benzworld on this issue, back in 2010. It was in the amg section. The dude's wiring harness was fried where the plug meets the knock sensor. Mybe next weekend i can split and redo all said affected wiring if this is the case. Still have some parts in the works. I can say that my cam position sensor wiring is not of the best quality and that be from a electrician. With that said I'm going to look at redoing my harness from scratch. I do know of specific products where i can reuse the original wiring. Just put a different coating on it and seal it differently. And most of all reroute some of it. OMG!! But it can be done in a few days.

[Vetruck]

In my most getto fashion, I shall reiterate what fucking morons Mecedes-Benz executives are for allowing the use of cheap ass biodegradable wiring in the first place, and then what fucking low life money grubbing ass lickers they are for swindling there way under a the legal statue of limitation as to not issue a recall and simply send a message to all old Mecedes owners they give a rats ass about us.

FUCK YOU MERCEDES BENZ

[Vetruck]

and FUCK YOU STEVE CANNON



there, I feel better.

[taz069]

Lmfao!! Going to chime in a lil!! Ve to my understanding for this short term of dealing with this issue. That the knock sensors deal with fuel pressure applied to the rail system, and they deal with timing also. It's a computer vs computer . Say the cam position sensor is telling the computer I need +15 degrees(via throttle position, maf readings, intake temps) in timing advance , and the knock sensor is telling the computer I need a -17 degree in timing by way I'll adjust fuel pressure in the mean time. This is a totally new issue to me and still with the said problems we have these cars!! It would be best for me just to pull the old wiring harness and just rebuild it. Now that I have the car tagged and insured I no longer have the extra cash to throw at it. With that said I still have the front lower bushings to contend with. I just wish I could get my hands on the original owner and some mercedes engineers! And drag them behind my better than new c280!! Cause I have no degree (college) I have a will and determination to see this thru!! I dang sure should have kept my mouth shut now the rear bearings are gonna go out!! ROTFLMAO!!! Still beats a new car payment!!

[Vetruck]

Still beats a new car payment!!
Quote the fact- you got that right.

[taz069]

Be safe friend! Keep in mind that's why we were built!! We can do better than any engineering dept!! And heaven forbid if we had their design experience! Me for one do understand that the Mercedes factory took up American standards in 95-98. And hence pass the buck and used susubstandard material's (I.e it will break down outside of warrenty) recall issues could not have been adressed until well outside of a specific guideline. I still have my grandmothers 66 c-10 Chevy. And that booger shoot it some gas and it will run!! No cars or truck nowadays will last that long!

[bpeter]

Vetruck

Can you confirm if you rebuilt the wiring on the tb or replaced the entire tb unit.

[Vetruck]

Vetruck

Can you confirm if you rebuilt the wiring on the tb or replaced the entire tb unit.

I bought a brand new complete TB unit with the entire new wire harness attached all as one unit. It is a VDO unit. I have a 4 cylinder C220 and it was just shy of $600 shpped to my doorstep.

[Vetruck]

These guys were less expensive but would have taken a few more days. I had mine overnighted from anther company that had it on their shelf and got it right out to me immediately.

Here is the best price I found if you can wait a few days for shipment.
http://www.new-part.com/product/mercedes-w202-c220-1994-1996-fuel-injection-throttle-body-idle-sped-actuator-vdo?gclid=CIfx5OqN37gCFS9dQgodziMAjw

[bpeter]

Thank you for your quick reply. The symptoms that my C220 exhibits are somewhat similar but not that frequent. It occasionally (once per week) stalls on only very hot days. It has so far only happened when the outside temperature was over 90F. When it is colder (e.g. morning and evenings), it never happens. The engine temperature is in the normal range 85-100C (I replaced the thermostat about 20K miles ago). When it is very hot outside, the engine seem like it does not have all the power it should have. I checked the intake air temperature sensor readings yesterday using the OBDII reader and it showed 137F while the outside air temperature was about 80F. I was idling in the parking lot when checking. I know the air will heat up a little bit before it gets to the IAT sensor (the reading seemed a bit high to me, but the guy at AutoZone thought it is often around 130 b/c of the engine heat).

Let me know your thoughts about this or other items to check. I have not checked the wiring on the TB (it is probably still original).

Some items that I have replaced over time are the fuel pump (original Bosch), fuel filter and fuel relay about 15K miles ago. The new Bosch remanufactured MAF sensor and spark plugs have about 2K miles on it. Checked air filter (looked clean- it was replaced about 10K miles ago).

[Vetruck]

bpeter, when you start the car in the morning (first start after sitting for a while) will the car start right up and die a few times and then finally stay running after the 2nd, 3rd or 4th attempt? That was a symtom I had for 6 months when I bought this car. I thought it lacked possibly a bad coldstart injector of something, but when I changed the TB this completely went away and the cars starts perfec tthe first time every time. It used to act alot like it was very cold blooded and had to sit and warm up for a while before you tried to move it, now I can put it in gear immediately and ilde it out of the garage without it dieing or stumbling like it was cold blooded.

hope that info helps with your diagnostics.

[Vetruck]

I also had about 3 or 4 incidences where I had to run recue my better half when she stopped somewhere and then came back out of a store to restart the car and nothing- like as it the overload protection relay or the fuel pump relay or something was going bad. I would open the truck and jiggle the little green box next to the battery adn then tried it and the car fired right up. strange, but I never replaced any of that and since th TB swap I have not had this issue either.

[bpeter]

It never happens in the morning when it is cold. I only see it happen after the car gets to its operating temperature and only on the days when it is really hot outside. So maybe I have a different issue. I can start a new thread and ask everyone if they have any suggestions.